1. Field of the Invention
The present invention relates to an optical pickup head used in a apparatus for recording, reproducing, or erasing information on an optical storage medium, and to an information recording/reproducing apparatus.
2. Description of Related Art
Optical memory technologies using optical storage media with a pit-shaped pattern, that are storage media of high density and large capacity, are increasingly adopted for digital audio disks, video disks, text file disks, and data files, for example. In recent years, high-density, large capacity optical storage media known as DVDs have been put into practical use and have garnered widespread attention as information media capable of handling large quantities of information, such as moving pictures. These DVD optical storage media are recorded and reproduced using a so-called red semiconductor laser that emits laser light of a wavelength near 650 nm.
A conventional optical pickup head in an optical disk system capable of recording and reproducing is described using FIG. 22.
A semiconductor laser light source 101, serving as the light source, emits a linearly polarized divergent beam 700 with a wavelength xcex2 of 650 nm. The divergent beam 700 emitted from the semiconductor laser light source 101 is incident on a diffraction grating 510 and split into three beams of zero order, xe2x88x921st order, and +1st order diffracted light. The zero order diffracted beam is a main beam 700a for recording/reproducing information and the +1st and xe2x88x921st order diffracted beams are sub-beams 700b and 700c used in a differential push-pull method (hereinafter, referred to as DPP) to detect tracking error (hereinafter, referred to as TE) signals stably. The ratio of the diffraction efficiency of the zero order diffracted beam to either one of the 1st order diffracted beams is ordinarily set from 12:1 to 20:1, and here it is 20:1. Accordingly, the sub-beams 700b and 700c are prevented from affecting the main beam 700a, and unintentional recording on an optical storage medium 410 can be avoided.
The three beams created by the diffraction grating 510, that is, the main beam 700a and the sub-beams 700b and 700c, pass through a polarizing beam splitter 520 and are converted into parallel beams by a collimating lens 530 with a focal length of 15 mm. The parallel beams pass through a quarter wavelength plate 540 and are converted into circularly polarized light, after which they are converted into convergent beams by an objective lens 560 with a 3 mm focal length. The opening of the objective lens 560 is restricted by an aperture 550, and its numerical aperture NA is 0.6.
The optical storage medium 410 is provided with a transparent substrate 410a and an information recording plane 410b, and the thickness of the transparent substrate 410a is 0.6 mm. The convergent beam from the objective lens 560 passes through the transparent substrate 410a and is focused on the information recording plane 410b. 
FIG. 23 shows the relationship between the tracks and the beams on the optical storage medium. As shown in FIG. 23, tracks, which are a plurality of continuous grooves, are formed on the information recording plane 410b of the optical storage medium 410 (FIG. 22). Tracks Tmxe2x88x921, Tm, and Tm+1 are lined up in order, and the track pitch P2, which is the distance between the track Tmxe2x88x921 and the track Tm and between the track Tm and the track Tm+1, is 0.74 xcexcm. The beams are arranged such that when the main beam 700a is positioned on the track Tm, the sub-beams 700b and 700c are positioned between the tracks Tm and Tmxe2x88x921 and the tracks Tm and Tm+1, respectively. Consequently, there is a 0.37 xcexcm wide spacing L2 between the main beam 700a and the sub-beams 700b and 700c in the direction perpendicular to the track Tm.
The main beam 700a and the sub-beams 700b and 700c focused on the information recording plane 410b are reflected, and after passing through the objective lens 560 and the quarter wavelength plate 540 and being converted into linearly polarized light with a polarization that is rotated by 90xc2x0 with respect to that of the incident path, they pass through the collimating lens 530 and are converged into convergent light. This convergent light is reflected by the polarizing beam splitter 520, passes through a cylindrical lens 570, and is incident on an optical detector 300. Astigmatism is imparted on the main beam 700a and the sub-beams 700b and 700c when they pass through the cylindrical lens 570.
The optical detector 300 has eight light receiving portions 300a, 300b, 300c, 300d, 300e, 300f, 300g, and 300h. The light receiving portions 300a, 300b, 300c, and 300d are for receiving the main beam 700a, the light receiving portions 300e and 300f are for receiving the sub-beam 700b, and the light receiving portions 300g and 300h are for receiving the sub-beam 700c. The light receiving portions 300a, 300b, 300c, 300d, 300e, 300f, 300g, and 300h each output a current signal corresponding to the amount of light received.
Using each of the signals output from the light receiving portions 300a, 300b, 300c, and 300d for receiving the main beam 700a, it is possible to obtain focus error (hereinafter, referred to as FE) signals through the astigmatism method, TE signals through a phase difference method, TE signals through a push-pull method, and information (hereinafter, referred to as RF) signals recorded on the optical storage medium. Also, when recording/reproducing continuous groove disks such as DVD-RW disks, TE signals can be obtained through DPP by jointly using the signals output from the light receiving portions 300e, 300f, 300g, and 300h for receiving the sub-beams 700b and 700c. After being amplified to a desired level and phase compensated, the FE signals and the TE signals are supplied to actuators 910 and 920, and based on these signals, focusing and tracking control are performed.
In DVDs, ROM disks for read only are standardized as two-layered disks provided with two information planes. Information can be read out from these two-layered disks without any problems by detecting the TE signals through the phase difference method using the conventional optical pickup head.
Moreover, at the research and development level, there have been many publications of research results for two-layered recordable disks having two information recording planes (hereinafter, referred to as two-layered recording disks). Initially, no information is written on two-layered recording disks, so TE signals cannot be detected by a phase difference method. For this reason, the TE signals are detected by DPP, as is the case with single-layered recordable disks.
However, even if two-layered recording disks are used with the above-mentioned conventional optical pickup head and TE signals are detected by DPP, there is the problem that letting the objective lens perform tracking generates an uncorrectable offset in the TE signals.
This is because when information is recorded/reproduced with one of the information recording planes of the two layers (hereinafter, that information recording plane is referred to as the focus plane), a portion of the beam forming a focal point on the focus plane is reflected and a portion passes through the focus plane and arrives at the other information recording plane (hereinafter, that information recording plane is referred to as the non-focus plane). This beam is out of focus on the non-focus plane and is reflected by the non-focus plane toward the optical detector. The beam reflected by the non-focus plane cannot be fully cancelled during detection of the TE signals by DPP due to aberration and variations in the amount of beam light, for example. For this reason, tracking with the objective lens leads to fluctuations in the amount that cannot be cancelled and an uncorrectable offset is caused in the TE signals.
This results in displacement from the track and partially erases information recorded on adjacent tracks when recording information to the optical storage medium, which causes the problem that information recoded on the optical storage medium can no longer be read out with fidelity.
It is an object of the present invention to provide an optical pickup head with which offset is not caused in the TE signals even when tracking with the objective lens in a case where a two-layered recording disk is used. It is a further object of the present invention to provide an information recording/reproducing apparatus using this optical pickup head.
An optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted by the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching the plurality of beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams and sub-beam light receiving portions for receiving first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the amount of light of the first or higher order diffracted beams focused by the converging means when they are substantially focused on and reflected by a focus plane of the plurality of information recording planes is equal to or greater than the amount of light of the zero order diffracted beam focused by the converging means when it is reflected without focusing thereon by a non-focus plane other than the focus plane of the plurality of information recording planes. Thus, there is the effect that even if a two-layered disk is used for the optical recording medium, there is no offset generated in the tracking error signals, even during tracking with the objective lens.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted by the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical storage medium has a plurality of information recording planes, guide grooves are formed in at least one of the information recording planes, and information is recorded on the guide grooves or between the guide grooves; and the relationship 10xc2x7xcex7sxe2x89xa7xcex7m is fulfilled, where xcex7m is a diffraction efficiency of a zero order diffracted beam of the diffracted beams created by the diffracting means and xcex7s is a diffraction efficiency of first or higher order diffracted beams.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted by the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams, and sub-beam light receiving portions for receiving first or higher order diffracted beams, of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and all of the sub-beam light receiving portions are arranged within the image formed on the optical detecting means by the light of the zero order diffracted beam focused by the converging means that is reflected without focusing by the non-focus plane of the plurality of information recording planes.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted by the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams and sub-beam light receiving portions for receiving first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the relationship S1xe2x89xa64xc2x7xcfx80xc2x7(dxc2x7NAxc2x7xcex1)2xc2x7xcex7s/xcex7m is fulfilled, where xcex7m is a diffraction efficiency of a zero order diffracted beam of the diffracted beams created by the diffracting means and xcex7s is a diffraction efficiency of first or higher order diffracted beams, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is an area of one sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted by the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams and sub-beam light receiving portions for receiving first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes, and guide grooves are formed in at least one of the information recording planes; and the relationship S1xe2x89xa64xc2x7xcfx80xc2x7(dxc2x7NAxc2x7xcex1)2xc2x7xcex7s/xcex7mxc2x7Rfo/Rdfo is fulfilled, where xcex7m is a diffraction efficiency of the zero order diffracted beam and xcex7s is a diffraction efficiency of first or higher order diffracted beams of the diffracted beams created by the diffracting means, Rfo is an effective reflectance of the focus plane among the information recording planes onto which the beam focused by the converging means substantially forms a focal point, Rdfo is an effective reflectance of the non-focus plane other than the focus plane of the plurality of information recording planes, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is one area of a sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium into two beams, an astigmatism imparting means for imparting astigmatism on a first beam branched at the beam branching means, a beam splitting means for further splitting a second beam branched at the beam branching means into two beams, a first optical detecting means for receiving the beam from the astigmatism imparting means and outputting a signal corresponding to the amount of light of the received beam, and a second optical detecting means for receiving the beams from the beam splitting means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical storage medium has a plurality of information recording planes, and guide grooves are formed into at least one of the information recording planes; and the beam splitting means splits the second beam in a direction parallel to the guide grooves.
It is also possible that the diffracting means creates a zero order diffracted beam and first or higher order diffracted beams, the first beam includes a zero order diffracted beam and the first or higher order diffracted beams, the first optical detecting means has four light receiving portions, and the zero order diffracted beam and the first or higher order diffracted beams are received by the light receiving portions overlappingly.
It is also possible that the first optical detecting means and the second optical detecting means each have light receiving portions for receiving the plurality of diffracted beams that have been focused, and all of the light receiving portions of the first optical detecting means and the second optical detecting means are arranged within the images that are formed on the first optical detecting means and the second optical detecting means by the light of the zero order diffracted beam focused by the converging means that is reflected without forming a focal point by the non-focus plane of the plurality of information recording planes.
Further, the beam splitting means can include a diffraction element.
Further, the beam splitting means can include a prism.
Further, the beams can be imaged substantially in focus on the first optical detecting means and the second optical detecting means.
Further, the size of the light receiving portions can be not less than three and not more than ten times that of an Airy disk.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a zero order diffracted beam and first or higher order diffracted beams from the beam emitted from the light source, a converging means for focusing the zero order diffracted beam and the first or higher order diffracted beams from the diffracting means onto an optical storage medium, a beam splitting means for respectively splitting into two beams the zero order diffracted beam and the first or higher order diffracted beams focused on the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams split by the beam splitting means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has a plurality of light receiving portions positioned lined up in a row; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the beam splitting means splits the beams with a splitting axis substantially parallel to the guide grooves.
Further, it is also possible that the light receiving portion for receiving the zero order diffracted beam of one of the beams split by the beam splitting means is positioned to be sandwiched between the light receiving portion for receiving the zero order diffracted beam of the other beam split by the beam splitting means and the light receiving portion for receiving the first or higher order diffracted beams of the other beam split by the beam splitting means.
Further, it is also possible that the spacing between the images formed on the optical detecting means by the zero order diffracted beam and the first or higher order diffracted beam of either one of the beams split by the beam splitting means is wider than the spacing between the images formed on the optical detecting means by the two zero order diffracted beams split by the beam splitting means.
Further, the beam splitting means can include a diffraction element.
Further, the beam splitting means can include a prism.
Further, the beams can be imaged substantially in focus on the optical detecting means.
Further, the size of the light receiving portions can be not less than three and not more than ten times that of an Airy disk.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium, an astigmatism imparting means for imparting astigmatism on the beams branched by the beam branching means, and an optical detecting means for receiving the beams imparted with astigmatism by the astigmatism imparting means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving the zero order diffracted beams and sub-beam light receiving portions for receiving the first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the relationship S1xc2x7xcex7mxc2x7Rdfo/(4xc2x7xcfx80xc2x7d2xc2x7NA2xc2x7xcex7sxc2x7Rfo)xe2x89xa6xcex1xe2x89xa6(Z0/2/xcex94z)1/2 is fulfilled, and xcex94z is in the range of three to ten times xcex/2/NA2, where Z0 is an astigmatic difference imparted by the astigmatism imparting means, xcex7m is a diffraction efficiency of the zero order diffracted beam and xcex7s is a diffraction efficiency of first or higher order diffracted beams of the diffracted beams created by the diffracting means, Rfo is an effective reflectance of the focus plane of the information recording planes onto which the beam focused by the converging means is substantially focused, Rdfo is an effective reflectance of the non-focus plane other than the focus plane of the plurality of information recording planes, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, xcex is a wavelength of the beam emitted from the light source, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is an area of one sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam splitting means for splitting beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium into two beams having different focal points, and an optical detecting means for receiving the beams split by the beam splitting means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams and sub-beam light receiving portions for receiving first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the relationship S1xc2x7xcex7mxc2x7Rdfo/(4xc2x7xcfx80xc2x7d2xc2x7NA2xc2x7xcex7sxc2x7Rfo)xe2x89xa6xcex1xe2x89xa6(Z0/2/xcex94z)1/2 is fulfilled, and xcex94z is in the range of three to ten times xcex/2/NA2, where Z0 is the spacing between the two focal points given the two beams split by the beam splitting means, xcex7m is a diffraction efficiency of the zero order diffracted beam and xcex7s is a diffraction efficiency of the first or higher order diffracted beams of the diffracted beams created by the diffracting means, Rfo is an effective reflectance of the focus plane of the information recording planes onto which the beams focused by the converging means are substantially focused, Rdfo is an effective reflectance of the non-focus plane other than the focus plane of the plurality of information recording planes, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, xcex is a wavelength of the beam emitted from the light source, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is an area of one sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam splitting means for splitting the plurality of diffracted beams focused on the optical storage medium and then reflected by the optical storage medium into two beams, an optical detecting means for receiving the beams split by the beam splitting means and outputting a signal corresponding to the amount of light of the received beams, and an astigmatism imparting means for imparting astigmatism on beams on their path from the optical storage medium to the optical detecting means; wherein the optical detecting means has main beam light receiving portions for receiving the zero order diffracted beams and sub-beam light receiving portions for receiving the first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a substrate of refractive index n and a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the relationship S1xc2x7xcex7mxc2x7Rdfo/(4xc2x7xcfx80xc2x7d2xc2x7NA2xc2x7xcex7sxc2x7Rfo)xe2x89xa6xcex1xe2x89xa6(Z0xc2x7n3/xcex94t/(n2xe2x88x921)/NA2)1/2 is fulfilled, and xcex94t is in the range of five to thirty times xcex/NA4, where Z0 is an astigmatic difference imparted by the astigmatism imparting means, xcex7m is a diffraction efficiency of the zero order diffracted beam and xcex7s is a diffraction efficiency of the first or higher order diffracted beams of the diffracted beams created by the diffracting means, Rfo is an effective reflectance of the focus plane of the information recording planes onto which the beams focused by the converging means substantially form a focal point, Rdfo is an effective reflectance of the non-focus plane other than the focus plane of the plurality of information recording planes, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, xcex is a wavelength of the beam emitted from the light source, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is an area of one sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a first beam splitting means for splitting the beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium into two beams, an optical detecting means for receiving the beams split by the first beam splitting means and outputting a signal corresponding to the amount of light of the received beams, and a second beam splitting means for splitting the beams on an optical path from the optical storage medium to the optical detecting means into two beams of different focal points; wherein the optical detecting means has main beam light receiving portions for receiving the zero order diffracted beams and sub-beam light receiving portions for receiving the first or higher order diffracted beams of the plurality of diffracted beams that are focused; the optical storage medium has a substrate of refractive index n and a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the relationship S1xc2x7xcex7mxc2x7Rdfo/(4xc2x7xcfx80xc2x7d2xc2x7NA2xc2x7xcex7sxc2x7Rfo)xe2x89xa6xcex1xe2x89xa6(Z0xc2x7n3/xcex94t/(n2xe2x88x921)/NA2)1/2 if fulfilled, and xcex94t is in the range of five to thirty times xcex/NA4, where Z0 is the spacing between the two focal points given the two beams split by the second beam splitting means, xcex7m is a diffraction efficiency of the zero order diffracted beam and xcex7s is a diffraction efficiency of the first or higher order diffracted beams of the diffracted beams created by the diffracting means, Rfo is an effective reflectance of the focus plane of the information recording planes onto which the beams focused by the converging means substantially form a focal point, Rdfo is an effective reflectance of the non-focus plane other than the focus plane of the plurality of information recording planes, NA is a numerical aperture of the optical storage medium side of the converging means, xcex1 is a lateral magnification of an optical system on a return path from the optical storage medium to the optical detecting means, xcex is a wavelength of the beam emitted by the light source, d is an optical spacing between two information recording planes of the optical storage medium, and S1 is one area of sub-beam light receiving portion.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam splitting means for splitting a plurality of beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams split by the beam splitting means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical storage medium has a plurality of information recording planes and guide grooves are formed in at least one of the information recording planes; and the semiconductor laser light source is formed on a substrate positioned such that it is substantially parallel to the guide grooves formed in the one or more information recording planes, and emits spontaneously emitted light from a location different from the location from which the laser beam is emitted.
Further, the substrate of the semiconductor laser light source can be made of sapphire.
Further, the substrate of the semiconductor laser light source can be made of gallium nitride.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, and an optical detecting means for receiving the beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has main beam light receiving portions for receiving zero order diffracted beams and sub-beam light receiving portions for receiving first or higher order diffracted beams of the plurality of diffracted beams that are focused; and dummy light receiving portions for preventing cross-talk between the main beam light receiving portions and the sub-beam light receiving portions are provided between the main beam light receiving portions and the sub-beam light receiving portions.
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, and an optical detecting means for receiving beams of the plurality of diffracted beams focused onto the optical storage medium and reflected by the optical storage medium and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has two main beam light receiving portions for receiving the zero order diffracted beams and four sub-beam light receiving portions for receiving the first or higher order diffracted beams of the plurality of diffracted beams that are focused; and when T1 and T2 are the signals output from the main beam light receiving portions and T3, T4, T5, and T6 are the signals output from the sub-beam light receiving portions, then tracking error signals are detected by calculating (T1xe2x88x92T2)/(T1+T2)xe2x88x92k[{(T3xe2x88x92T4)+(T5xe2x88x92T6)}/(T1+T2)] (wherein k is a constant).
Another optical pickup head of the present invention is provided with a light source for emitting a light beam, a diffracting means for creating a plurality of diffracted beams from the beam emitted from the light source, a converging means for focusing the plurality of diffracted beams from the diffracting means onto an optical storage medium, a beam branching means for branching a plurality of beams of the plurality of diffracted beams focused on the optical storage medium and reflected by the optical storage medium, and an optical detecting means for receiving the beams branched at the beam branching means and outputting a signal corresponding to the amount of light of the received beams; wherein the optical detecting means has two light receiving portions; the optical storage medium has a first information recording plane and a second information recording plane and guide grooves are formed in the first information recording plane; and wherein, if the diffracted beams focused by the converging means form a focal point on the first information recording plane and do not form a focal point on the second information recording plane, then tracking error signals are detected by calculating (Tf1+Ts1xe2x88x92Tf2xe2x88x92Ts2)/(Tf1+Ts1+Tf2+Ts2) and a relationship Tf1+Tf2xe2x89xa75xc2x7(Ts1+Ts2) is fulfilled, wherein Tf1 and Tf2 are signals output from the two light receiving portions when the beams reflected by the first information recording plane are received by the optical detecting means, and Ts1 and Ts2 are signals output from the two light receiving portions when the beams reflected by the second information recording plane are received by the optical detecting means.
Further, a first light focusing means for converging the beams received by the first optical detecting means is provided on the light path from the optical storage medium to the first optical detecting means, a second light focusing means for converging the beams received by the second optical detecting means is provided on the light path from the optical storage medium to the second optical detecting means and the first and second light focusing means have a convex lens and a concave lens respectively.
Further, a light focusing means for converging the beams received by the optical detecting means is provided on the light path from the optical storage medium to the optical detecting means, and the light focusing means has a convex lens and a concave lens.
An information recording and reproducing apparatus of the present invention is provided with an above optical pickup head, a drive portion for changing the relative position between the information storage medium and the optical pickup head, and an electric signal processing portion for receiving signals output from the optical pickup head and performing calculations to obtain desired information.